The delivery of pharmaceutically active agents by way of dermal patches has become increasingly popular in recent years. Dermal patches are often employed when it is desired to obtain a controlled release of a pharmaceutically active ingredient over time, e.g. from several hours to several days or weeks. In addition, dermal patches are often utilized to deliver a pharmaceutically active agent to a specific area of the skin. Notable recent uses of dermal patches have been in, for example, the transdermal delivery of nicotine which has been helpful for some humans to curb the urge to smoke.
Typically, dermal patches used for the delivery of a pharmaceutically active agent to the skin comprise an internal reservoir or a polymer matrix as a carrier for the pharmaceutically active agent which is supported by protective skins, e.g., polyethylene, for structural integrity. Although such dermal patches typically function well when in contact with intact, unbroken skin, they often offer little or no significant benefit when used in contact with open skin, e.g., lacerated, burned or blistered skin.
Polymeric gels based on hydrated polymers have been proposed for use in treating lacerations, burns and blisters on the skin. Such polymeric gels are typically cross linked to provide structural integrity. However, typical cross linking techniques have disadvantages associated therewith. For example, gamma irradiation has been used to gel aqueous polymer solutions which can provide a gel having adequate structural integrity. Such irradiated gels may be physiologically compatible. However, the irradiation can delitirously affect any pharmaceutically active agents present in the gel. Therefore, they are unsuitable for delivery of pharmaceutically active agents. Gels cross linked with aldehydes, such as, formaldehyde, or glutaraldehyde have also been proposed. However, gels cross linked with such aldehydes may not be physiologically compatible and therefore may not be suitable for use in contact with skin. In addition, boric acid, and sodium tetraborate have been proposed to gel polymeric solutions. This reaction, however, necessitates a pH of 9 or greater which is not desirable for use in contact with skin.
Accordingly, dermal patches which are physiologically compatible, suitable for use in contact with open skin and able to carry and deliver a pharmaceutically active agent are desired.